remove listen note since it seems to have gone away

[Ankur Sethi]

Keeping content here if needed later.

#### Note:

If you get an error

        ** ERROR: directory is already being watched! **

        Directory: bpmn/java_app/src/main/resources
        is already being watched through: bpmn/diagrams

        MORE INFO: https://github.com/guard/listen/wiki/Duplicate-directory-errors

It is because `rails generate camunda:spring_boot` creates a symlink inside your application folder at
`bpmn/resources` which points to the resources folder of the spring boot app. Normally the bpmn folder should not listened to
but ActionMailer preview causes test/mailers/previews to get added to the Rails EventedFileChecker
by default. RSpec is supposed to override it, but it is not appropriately overridden for EventedFileChecker
and/or you don't have spec/mailers/preview existing. So if test/mailers/previews does not exist, it goes to the first common directory
that exists, which is your Rails root folder (if you don't have test/mailers either). So EventedFileChecker is listening to your 
entire Rails folder instead of only Ruby source folders. Not a big problem, but it causes a problem for our created symlink.

So add:

        config.action_mailer.show_previews = false

to your `development.rb` file to solve listen errors about a symlink. Unless you are using ActionMailer
previews, in which case you should have the directory created already.